1. Field
The present disclosure relates generally to techniques using Multiple Input Multiple Output (MIMO) antenna schemes and, more specifically, to techniques employing MIMO and Orthogonal Frequency Division Multiplexing (OFDM) to transmit data.
2. Background
Currently, there is interest in multiple-antenna systems, such as Multiple Input Multiple Output (MIMO) systems, where two or more devices communicate with each other, each using more than one antenna, in order to enhance data transmission. Some multiple-antenna systems increase throughput and/or quality by exploiting spatial multiplexing and/or antenna diversity to send the same data on separate signals or to create a phased array to send data.
Evolution Data Optimized (EVDO) is a telecommunications standard promulgated by the 3rd Generation Partnership Project 2 as part of the CDMA2000 family. EVDO facilitates high data rates in wireless networks. EVDO has gone through several evolutions, the current revision of which provides for a forward link using Time Division Multiple Access (TDMA) principles to transmit data sub-streams on multiple carriers (tones). Current revisions of EVDO, however, do not take advantage of MIMO capabilities, which may be available in some mobile devices. It would be desirable to provide users having MIMO capabilities with the opportunity to use such capabilities in an EVDO network, while also supporting users who lack MIMO capability, i.e., having backward compatibility.
Orthogonal Frequency Division Multiplexing (OFDM) is a technology that transmits data on multiple, orthogonal sub-carriers, each of the sub-carriers corresponding to a parallel data stream. OFDM has found use in conventional data systems, such as Enhanced Broadcast and Multicast Services (Enhanced BCMCS). However, while Enhanced BCMCS provides for multi-cast and broadcast functionality, EVDO provides for unicast functionality. Moreover, the Enhanced BCMCS incorporating OFDM do not support MIMO. Currently, there is no unicast system available that incorporates the advantages of OFDM and MIMO into a TDMA forward link, while remaining backward compatible with earlier revisions.